1. Field of the Invention
The present invention relates to a liquid jet recording head, for a liquid jet recording system, that for recording discharges, through fine discharge ports, droplets of a recording liquid and attaches the recording liquid to a recording medium, such as a recording paper sheet, and to a method for assembling such a recording head. In particular, the present invention pertains to a liquid jet recording head that includes a pressing member for securing, under pressure, a member in which are formed a plurality of discharge ports and liquid flow paths, and to a method for assembling such a recording head.
2. Related Background Art
Generally, a conventional liquid jetting recording head comprises: a plurality of fine discharge ports, through which a recording liquid is discharged; liquid flow paths, which communicate with the individual discharge ports; and discharge energy generating elements, which are located along the individual liquid flow paths. This recording head is so designed that a driving signal corresponding to recorded information is applied to the discharge energy generating element, and discharge energy is exerted to propel a recording liquid along a liquid flow path corresponding to the pertinent energy generating element, so that droplets of the recording liquid are ejected through the discharge ports for printing.
A liquid jet recording head of this type is constituted by an element substrate and a grooved top plate. A plurality of discharge energy generating elements (electro-thermal converting elements, etc.), which are precisely formed using a semiconductor manufacturing technique, are arranged on the element substrate. And accurately formed on an orifice plate and/or the grooved top plate, using a precise manufacturing means, such as a laser process means, are a plurality of discharge ports; a plurality of liquid flow path grooves, which communicate with the individual discharge ports; a common liquid chamber, which communicates with the flow path grooves; and a liquid reservoir. The element substrate and the grooved top plate are then arranged and bonded together, so that the discharge energy generating elements on the element substrate are aligned with corresponding flow paths and discharge ports in the grooved top plate. Following this, a pressing member, such as a spring, is used to apply pressure to the resultant structure, so that a uniform bonded condition is acquired in the vicinity of the discharge ports, and the element substrate and the grooved top plate are firmly secured to each other.
When assembling the element substrate, the grooved top plate and the pressing member, the energy generating elements, the discharge ports and the liquid flow path grooves must be aligned precisely, in micron order. Disclosed in Japanese Patent Application Laid-open Nos. 04-171130, 04-171126, 04-171163 and 05-004136 are well known liquid jet recording head manufacturing methods that provide for the precise alignment and the assembly of the element substrate and the grooved top plate. According to these manufacturing methods, to assemble an apparatus, first, the positions of the discharge energy generating elements formed on an element substrate are identified and stored as images. Then, a grooved top plate, in which discharge ports and liquid flow path grooves are formed, is temporarily mounted on the element substrate. The positions of the discharge ports and of the flow path grooves are compared with those of the discharge energy generating elements, and the relative positioning of the element substrate and the grooved top plate relative is adjusted to align the discharge energy generating elements with the discharge ports and the liquid flow path grooves. In addition, to prevent any change in the positional relationship, an ultraviolet setting adhesive is used to temporarily secure the grooved top plate to the element substrate. In the succeeding procedure, a pressing member, such as a spring, is assembled with the temporary unit comprising the element substrate and the grooved top plate in order to firmly bond to each other the faces of the element substrate and the grooved top plate.
The use of the pressing member can be dispensed with, and an adhesive can be applied to securely bond the element substrate to the grooved top plate; however, the adhesive may run and enter the liquid flow paths, and thereby change the chemical composition of the ink that is used as the recording liquid, or it may adversely affect and deteriorate the liquid ejection performance.
A liquid jet recording head using a pressing member is disclosed in, for example, Japanese Patent Application Laid-open No. 4-247953. In this publication, the pressing member is extended in the direction in which discharge ports are arranged, and is constituted by a pressing portion that applies pressure in the vicinity of the discharge ports in a grooved top plate, a U-shaped flexible portion that urges the pressing member in the direction in which the grooved top plate and a substrate element are bonded, and an engagement portion that is provided on both sides of the U-shaped flexible portion and engages a base plate. According to a method that uses the pressing member to secure the grooved top plate to the element substrate, the pressing member is bent and charged by supporting the portion of the U-shaped flexible portion that is near the pressing portion. In this state, the element substrate and the grooved top plate are assembled with the base plate that is temporarily fixed to the grooved top plate. Then, the pressing member is released so that the pressing portion of the pressing member can apply pressure to the grooved top plate, and the grooved top plate and the element substrate are joined together.
Recently, the precision provided by liquid jet recording apparatuses has increased, and a need has been expressed for improvements in the accuracy with which the discharge ports of liquid jet recording heads are positioned and in the exactness with which liquid droplets land on recording paper.
In order to improve the exactness with which liquid droplets land when they are ejected by a liquid jet recording head that comprises an element substrate, which is fixed to a reference member formed on a base plate, a grooved top plate, which is to be bonded to the element substrate and in which are formed a plurality of liquid flow path grooves corresponding to discharge energy generating elements and a plurality of discharge ports through which a recording liquid is discharged, and a pressing member, for forcing together the grooved top plate and the element substrate, the conditions, such as precision and stability, under which the grooved top plate and the substrate element are bound together must be improved.
However, for the conventional liquid jet recording head described above, in the procedure in which pressure is used to bond the grooved top plate to the element substrate, the following problems still remain. (1) Since the element substrate and the grooved top plate are temporarily fixed together using an ultraviolet setting adhesive, the accuracy with which these components are secured to each other may be changed due to a reduction in the volume of the adhesive after it is set, and a defect may occur that affects the precision that is currently requested for a recording head. Further, since the element of which the ultraviolet setting adhesive is composed melts in the ink that constitutes the recording liquid for the recording head, the composition of ink is changed and deterioration of the printing quality occurs. In addition, part of the projected ultraviolet rays used to set the adhesive may leak out, and may adversely affect the vision of workers in the vicinity. Furthermore, since to set the adhesive the ultraviolet rays must be projected for a predetermined period of time, and since the tact of the apparatus must be extended to install a light source for the ultraviolet irradiation, the cost of the apparatus is increased. (2) In order to assemble the pressing member with the base plate, the pressing member must be in the charged state because it must not contact the grooved top plate that was previously positioned. However, if the pressing member is in the charged state too long, the pressing force provided by the pressing member will be reduced and the pressing portion may be deformed. Therefore, the length of time the pressing member is held in the charged state should be as short as possible.